Phase failure and phase reversal protective device



Sept. 15, 1931.

'E. ,1. POSSELT 1,823,211

PHASE FAILURE AND PHASE REVERSAL PROTECTIVE DEVICE Filed Oct. 21. 1929Patented Sept. 1s, 1931 UNITED STATES PATENT OFFICE.

EDWARD J. POSSELT, OF MILWAUKEE, WISCONSIN, ASSIGNOR 1'0 CUTLER-HAMMER,INC., 01' MILWAUKEE, WISCONSIN, A CORPORATION OF DELAWAQE PHASE FAILUREANI) PHASE REVERSAL PROTECTIVE DEVICE Application filed October 21,1929. Serial No. 401,183.

This invention relates to low voltage, hase failure and phase reversalprotective devices for polyphasealternating current circuits.

Devices embodying electromagnetically operated contactors in combinationwith impedances connected in a three wire polyphase circuit in starrelation and calibrated so as to close and remain closed while a givenphase relation and agiven voltage of the circuit is maintained and toopen when this phase relation changes or when the voltage of the circuitdecreases below a certain value, are known in the art. Such a device isdescribed in the Stevens application Serial No. 286,262 assigned to thesame assignee. While the Stevens device meets the average operatingconditions, the sensitivity to operate upon unbalancing of the phases orupon voltage reduction is such that where used in connection with dynamoelectric machines which have inherently close regulation, the load onsuch machine may reach a considerable value before the device responds.

The present invention has among its objects that of providing animproved projective device embodying the foregoing principle andovercoming the aforementioned difficulties.

Other objects and advantages will hereinafter appear.

The accompanying drawings illustrate diagrammatically one embodiment ofthe invention and the same will now be described,

it being understood that the invention is capable ,ofembodiment in otherforms, falling within the scopeof the appended claims. 'Flg; 1 is a,diagrammatic illustration of one form-0f protective device used in con-.nection' witha dynamo electric machine, Fig.

2 is a-simplified diagram of certain ofthe I circuits shown inF ig- 1-,Fig. '3 is a vectordiagramofcerta-i'n voltages and Icurrents: of thesystem for normal; conditions of operation, Fig. :4 1s 'a. vectordiagram-of the condition of .phaseireversal, while Fig.5 is:.a vectord1agram= for failuretof'voltage in one of the.

phases. w; I Referring to Fig. 1, L, L and L are the supply lines of athree wire polyphase circuit which is provided with an electromagneticswitch 12 having actuating coil 13. This coil may be connected acrossany two of the supply lines and has connections which are controllableby an electroresponsive rela 9.

The relay 9 is provided with an operating winding 10 and contact members11. One end of the operating winding 10 is connected to line L while theother end is connected to the anode 2 of an electron tube 1 which may beof the high vacuum type and which is equipped with a heated filament. 3,supplied with current from the secondary winding 5 of a transformer 4having the primary winding 6. One end of the primary winding 6 isconnected to line L while the other end and one end of the secondarywinding 5 are connected to the common terminal of impedances 7 and 8which latter are connected in series between lines L and L Thus thetransformer primary winding 6 and the impedances 7 and 8 form a starconnected impedance system. The impedance 7 is hi hly inductive whilethe impedance 8 is preferably a pure ohmic resistance. As the coil 10 isconnected in series with the discharge path of the tube 1 between line Land the star point of the system,it forms a shunt path for thetransformer winding 6 and I proportion the circuit in such a way thatthe resultant impedance of the transformer and the Winding 10 plus thetube are of proper value to produce the desired result, namely that aslong as the phase relation and voltage of the system are normal asufiicient current flows through the winding cause relay 9 to open thecircuit of coil 13 of the circuit breaker; 12. and thus efi'ectdisconnection of the motor from. lines L L andL. The action. of thedevice. is as follows;

The impedance values of the various, circuits including the tube andthecoil 10 are selected so that during normal operation the voltageimpressed upon the winding 10 is a maximum. The voltage induced in thesecm E and E arethe voltages impressed upon under normal conditions. Thearrow indi-' cates the rotation of the voltage vectors as being in acounterclockwise direction. E,

the impedances 6, 7 and 8 respectively, ile I is the current flowingthrough the windings 6 and 10. The heating current of the filament '3 isobviously proportional to'the current I.

In case the phases should be reversed or one of the phases of the systemshould fail, the voltage impressed upon the primary winding 6 of thetransformer is reduced, thereby decreasing the temperature of thefilament 3, which results in an increase of the resistance of the tube.This causes a decrease of the current of the coil 10 and this current isfurther decreased due to the fact, that the voltage impressed upon thecircuit of the coil is reduced in the same proportion as the voltageimpressed upon the primary 6. Due to the cumulative action and the factthat the impedance of the tube varies with a higher power of the voltageimpressed upon the filament, the reduction of the voltage in the coil 10is relatively much greater than thereduction of the voltage impressedupon the corresponding'circuit and the device therefore reacts todisconnect the motor upon a very slight voltage reduction of the systemor upon unbalancing or phase reversal.

Fig. 4 is a vector diagram for reversal of phases so that the phaserotation is now clockwise, this condition obtaining if the phasesapplied to the terminals L and L are interchanged. It will be seen thatunder these conditions, the voltage E and the corresponding current Iare greatly reduced.

Fig. 5 is a vector diagram for failure of voltage in phase 1. In thiscase also the voltage E and the current I are reduced from the valuesobtaining under normal conditions as illustrated in Fig. 3.

It will of course be understood by those skilled in the art, thatinstead of employing -in uctances to produce currents which lag be indor lead the voltages in the respective circuits, condensers may beemployed, and in 55 eneral that the system is capable of a'numer ofmodifications all of which are within thescope of the appended claims. I

What I claim as new and desire to secure by Letters Patent is: 1. Aprotective device for polyphase circuits comprising a controlling devicefor said circuit including a space discharge tube, a star connectedsystem of impedances and means whereby said tube is caused to respond tochanges in a. voltage across certain of said tube in circuit with saidelectromagnet for impedances resulting from changes in the electricalconditions of said circuit,

2. A protective device for polyphase circuits comprising anelectromagnetic winding, a space discharge tube in circuit with saidwinding for controlling its current, a star connected system ofimpedances and means whereby said tube is caused to respond to changesin a voltage across certain of said impedances resulting from changes inthe electrical conditions of said circuit.

3. A protective device for polyphase circuits comprising a switch, anelectromagnet controlling said switch, a space discharge.

controlling the latter, a star connected system of impedances and means,whereby said tube is caused to respond to changes in a voltage acrosscertain of said impedances resulting from changes in the electricalconditions of said circuit.

4. A protective device for polyphase circuits comprising a controllingdevice for said circuit including a space discharge tube, a starconnected system of impedances and means whereby said tube is caused torespond to changes in voltage across certain of said impedancesresulting from variations. in voltage and/or changes in phase rotationof'said polyphase circuit. 1

5. A protective device for polyphase circuits comprising'a switch, anelectromagnet controlling said switch, a space discharge tube in circuitwith said electromagnet forv controlling the latter, a star connectedsystem of impedances and means whereby sald tube is caused to respond tochanges in' voltage across certain of said impedances resulting fromvariations in voltage and/or changes in phase rotation of said polyphasecircuit.

6. A protective device for polyphase circuits comprising a switch, anelectromagnet controlling said switch, a space discharge tube in circuitwith said electromagnet for controlling the latter, a transformer andtwo impedances, said transformer and saidimpedances being connected instar relatlon to said polyphase circuit-and means whereby said tube iscaused to respond to changes m the voltage across certain of said starconnected elements resulting from changes in the electrical condition ofsaid circuit.

7. A protective device for polyphase c1rcuits comprising an'electromagnetic switch, 2 a space discharge tube in circuit with theWinding of said switch to control its operation, a transfoTmer, an'inductance and a resistance, said transformer, inductance and resistancebeingconnected in star relationto said polyphase circuit and meanswhereby said tube is caused to respond to changes in voltage acrosscertain ofsaid star connected elements resulting from changes in theelectrical conditions of said circuit.

- 8. A protective device for polyphase circuits comprising anelectromagnetic switch, a

space disc arge tube in circuit with the winding of said switch tocontrol its operation, a

transformer, an inductance and a resistance,

said transformer, inductance and resistance being connected in starrelation to said lyphase circuit and means to cause said tum to respondto changes in voltage across certain of said star connected elementsresulting from variations in Volta e and/or changes in phase rotation ofsaid p yphase circuit.

9. A protective device for polyphase circuits comprising anelectromagnetic switch, a

space discharge tube in circuit with the windingof said switch tocontrol its operation, a transformer, an inductance and a resistance,said transformer, inductance and resistance being connected 1n starrelation to said polyphase circuit andmeans to cause said tube torespond to voltage variations of said transformer resulting. fromvariations in voltage and/or changes in phase rotation of said polyphasecircu1t;,

10. A protective device for polyphase circuits comprising a transformer,an inductance and a resistance connected in star relation to saidcircuit, a space discharge tube connected to said transformer so as torespond to voltage variations of the latter resulting from 1 variationsin voltage and/ or changes in base rotation of said polyphase circuit,sai tube being adapted upon response to control said polyphase circuit.I

11. A protective device for polyphase circuits comprising a transformer,an inductance and a resistance connected in star relation to saidcircuit, an electromagnetic switch, a

. space discharge tube having a heated cathode connected to thesecondary winding of said transformer, so as to res 0nd to voltagevariations of the latter r'esu tin from variations in voltage and/orchanges in phase rotation of said polyphase circuit and controlling said1 43 electromagnetic switch.

, 12. Apolyphase circuit, anelectromagnetic switch for controlling saidcircuit a star connected system consisting of a transformer,

an impedance and a resistance connected to said circuit, and athermionic tube having its cathode heated by the. secondary current ofsaid transformer and its anode connected in series with the winding ofsaid switch so as to respond to voltage variations impressedupon thetransformer resultingnfrom variations in voltage and/orchanges in phaserotation of sai polyphase circuit, to thereby control saidelectromagnetic switch,

In witness whereof, I' have hereunto sub- 6 scribed my name.

' EDWARD J. POSSELT.

